Tamoxifen is a synthetic non-steroidal ant estrogen. It was suggested to study the role of vitamin C in alteration of enzymes responsible of energy metabolism induced by administration of tamoxifen to mouse. The effect of tamoxifen and tamoxifen with vitamin C on some activity of enzymes in the mice representing glycolytic, gluconeogenic and glycogenolytic pathway and also, liver function enzymes represented by aspartate aminotransferase (AST), alanine amino-transferase (ALT), acid phosphatase (ACP) and alkaline phosphatase (ALP) were studied. The present results showed that a significant (p < 0.001) increase in glycolytic enzymes (HK, PK, GPI and PFK), gluconeogenic enzymes, G-6-Pase, acid phosphatase (ACP), alkaline phosphatase (ALP) and glucose, were observed in treated groups, while LDH, glycogen phosphorylase, AST and ALT enzymes activities showed significant (p < 0.01) reduction. The present results also, showed that significant reduction in glycogen, total protein, total cholesterol, uric acid, urea, and creatinine in treated mice as compared to the normal healthy control group. However, normal control mice treated with tamoxifen and vitamin C showed no side effects of most parameters compared to the normal healthy control group. It was concluded that vitamin C may prevent tamoxifen-induced testes toxicity in mice.